An analysis of the 170,000 cases discharged for disability in England showed that twenty per cent were due to war neuroses. In his second Lettsomian lecture Mott[96] called attention to the interesting similarity between shell shock following concussion and burial, and the symptoms resulting from an acute carbon monoxide poisoning. This was, of course, a very possible complication in trench warfare. The headache, ringing in the ears, blurred and indistinct vision, hallucinations of sight, or actual blindness, giddiness, yawning, weariness, vomiting, cold sensations, palpitation, sense of oppression on the chest, etc., so common in gas poisoning are often followed, when consciousness is regained, by confusion and loss of memory, with retrograde amnesia. Tremors and loss of speech are also frequently noted. Mott reached the conclusion that shell shock, in some cases at least, was due to gas poisoning. In his third Lettsomian lecture he discusses the symptomatology of shell shock. In some instances there was a partial loss of consciousness, characterized by dazed states somewhat similar to those of epilepsy. Under speech defects he includes mutism, aphonia, stammering, stuttering and verbal repetition. Headache in the occipital region was found to be a very common symptom. Vasomotor conditions were palpitation, breathlessness, pericardial pain, rapid weak pulse, low blood pressure, cold extremities, low temperature, etc. Anesthesia and hyperesthesia or loss of pain sense also occurred, and deafness was often observed. Smoky vision, photophobia and functional blindness were frequent eye symptoms. Tremors, tics, choreiform movements, functional paralysis and gait disturbances are also mentioned by Mott. In the Chadwick lecture he later called attention to the presence of insomnia and terrifying dreams in practically all cases of true shell shock.